The present invention relates to a device for cleaning ship's hulls and more particularly to a robotically operated device using ultrasonic means for the cleaning of ship's hulls.
Fuel savings of several hundred million dollars annually are expected from a pending Navy decision to use anti-fouling hull paints based on toxic tributylin compounds. Several Navy trials have demonstrated that these paints routinely out perform the current military specification paints based on cuprous oxide. Additional savings are expected as a result of less frequent dry-docking and the elimination of underwater hull cleaning. Current hull cleaning methods in just eight (8) Navy ship yards use 45,000 tons of abrasive that would have to be detoxified if used on the organic paint, and 180 million gallons of water that would have to be treated annually.
The organotin/tributylin paints have the capability of keeping the hull of a ship free of calcerous fouling for 5 to 7 years without underwater cleaning. Use of the paints would increase the operational availability of the Navy ships as well as commercial ships. The paints would also improve the operational readiness by maintaining the maximum speed and range of the ships over a much longer period of time due to the absence of calcerous fouling.
Satisfactory methods need to be developed to manage the organic waste during the application of the paint, removal of spent paints in dry-dock prior to repainting, and detoxification of the grit and other wastes generated during the present abrasive blasting method used.
There are presently three existing cleaning methods which are used for cleaning ship's hulls:
1. Chemical paint strippers are currently used to remove small patches on the holes required for non-destructive testing and access cuts. This method is unsuitable for cleaning the entire ship's hull.
2. Abrasive grit blasting is used for cleaning the entire hull, resulting in toxic wastes that could amount to 54,000 tons of grit per year that would have to be detoxified by some method, as well as over 180 million gallons of water that would have to be treated just from 8 Naval ship yards. Solid grit waste disposal methods presently being evaluated to manage organic paint wastes include landfill disposal and incineration.
3. An experimental High Pressure Cavitating Water Jet System (CWJS), using pressures of 10,000 to 15,000 psi in a special nozzle has been developed in a manual prototype. The prototype produced a 500 percent increase in efficiency over the chemical strippers used on the 5 foot by 6 foot hole patches. Attempts are being made by the Navy to scale up and robotize the system for cleaning the entire hull.
A search of the prior art failed to uncover any prior art references which disclose the robotic ultrasonic device for cleaning of ship's hulls of the present invention. One patent was uncovered which discloses an ultrasonic decontamination robot. The patent uncovered during the aforementioned search is as follows:
______________________________________ U.S. Pat. No. Inventor Issue Year ______________________________________ 4,595,419 Patenaude 1986 ______________________________________
While Patenaude is directed to an ultrasonic decontamination robot, the disclosed device is designed to remove radioactive contamination by ultrasonic induced cavitation in a fluid medium from the internal surface of the inlet and outlet headers, divider plate, tube sheet, and lower portions of tubes of a nuclear power plant steam generator. As such, the device of Patenaude is unsuitable for cleaning ship's hulls.